Installing bevel siding or clapboard on a house typically begins with mounting the starting clapboard on the bottom edge of the house. Then each additional clapboard is mounted above the previous with the lower part exposed ("to the weather") and the upper part covered slightly by the next higher clapboard. This is often done using a "story pole" which is made by marking a board or pole at intervals equal to the "to the weather" width. Then the story pole is held against the house sheathing at a number of places and the marks are transferred right onto the sheathing, to indicate where the bottom of each clapboard should be located. Or the story pole could be offset by the width of the overlap of the clapboard and then marked with the "to the weather" width intervals to enable the top of the clapboards to be the gauge point. When a window is encountered, if the bottom or top of the window does not align with a clapboard edge the clapboard is notched to accommodate the window. This is not only aesthetically unattractive, it also requires extra work in the measuring and cutting and careful handling of the notched clapboards, which increases the time and effort of installation.
If it is desired to install the clapboard so that it aligns neatly to the tops and bottoms of the widows without notching, then typically a measurement is taken from the bottom, starting, clapboard to the bottom of the first row of windows. That measurement is divided by the "to the weather" width which gives the number of clapboards needed to fill that area. The number is usually not a whole number. So that number is rounded off to the nearest whole number and divided into the original measurement to give a new "to the weather" width. This new "to the weather" width is the interval used in that area to set up the story pole which is used as before. This laborious process is repeated for each new area.